Final answer:
The couple's child has a 50% chance of having sickle cell anemia, as the mother is homozygous for the disease and the father is a heterozygous carrier. A Punnett square analysis reveals that two of the four possible genetic combinations result in sickle cell disease.
Step-by-step explanation:
Genetic Probability of Sickle Cell Anemia in Offspring
If a 25-year-old pregnant woman with sickle cell disease is concerned about the genetic health of her fetus, and her husband has been genetically tested and found to be a heterozygous carrier, one can determine the likelihood of their offspring having sickle cell anemia through a Punnett square. Sickle cell anemia is an autosomal recessive disease. This means that for a child to have this condition, they must inherit two copies of the mutant gene, one from each parent.
In the given scenario, since the mother has sickle cell disease, she has two copies of the sickle cell allele (homozygous). The father is heterozygous, meaning he carries one sickle cell allele and one normal allele. When creating a Punnett square for this couple, we have the following:
- The mother can only pass on the sickle cell allele (SS).
- The father can pass on either the sickle cell allele (S) or a normal allele (A).
This creates four possible combinations for their child:
- SS (Sickle Cell Disease)
- SA (Carrier)
- SS (Sickle Cell Disease)
- SA (Carrier)
As shown, there is a 50% chance the child will have sickle cell disease (inheriting SS), and a 50% chance they will be a carrier (inheriting SA). Therefore, the percent possibility of this couple's child having sickle cell anemia is 50%.